Telephone diaphragm



Jain. 13, 1925. 1,522,758

l P. THoMAs I TELEPHONE DIAPHRAGM Filed April 18, 1922 cal energy, andvice versa, ing the quality, tone and quantity @Pamesa am.. is, was;

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iszzgss PHILLIPS THOMAS, OF PITTSBURGH, IENNSYILV'AN'LB.,Y ASSIGNOR T0WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OFPENNSYLVANIA..

TELEPHONE DIAPHRAGM.

Application led April 18, 1922. Serial No. 555,272.

admit of the faithful translation of sound'` waves into correspondingmodulated electriwithout impairof the translated energy.

ln the present state of the art, diaphragms, as ordinarily made, consistof a :plain-circular disk of a desired material, as,` for instance,mica, paper or iron, depending upon the specic application.

lt is found that such diaphragms have, in addition to the frequency atwhich the diaphragm as a whole is resonant, other frequencies at `whichpartial' resonance occurs. Furthermore, it has been found that if thediaphragm is not a perfect plane, or lif there are sections in whichthere are kinks or wavy places, each of such places will cause partialresonance at some frequency other than the natural frequency of thetdiaphragm as a whole. K

Withthe diaphragm embodying the above mentioned defects, it is apparentthat distor tion is introduced, which greatly impairs the usefulness ofsuch transmitters for certain classes of work, as, for instance, thetransmission of music by wireless telephony.

According to my invention, l compensate for the distorting effectscaused by the fundamental resonant frequency of the diaphragm byemploying a diaphragm which has a lower resonant frequency than thelowest note tobe employed. Such dia' phragms, however, have' thedisadvantage of having segmental vibration periods which result in theemphasis of certain tones and hence cause distortion.

To overcome the latter defect and others hereinbefore mentioned, lprovide the diaphragm with corrugations which are disposed inconcentricv circles `from the center ,of the diaphragm. outwards. Eachcircle, if no others were present, would cause partial resonance at somefrequency. However, by makingthe radii of the circles of such relativelengths that the numerical `expressions thereof are prime to each .otherand impressing a considerable number on the diaphragm, each corrugationwill annul, -in a great measure, thetendency Jto resonance due to thecircles on each side thereof. Thus,I am enabled to produce a diaphragmhaving no resonant frequencies except the one low frequency at whichthe' diaphragm vibrates as a unit. y

` An advantage of such'construction is that it leaves but one resonancepoint to be corrected instead of a number, as is the case with a plaindiaphragm and, in addition, the act of impressing the corrugations onthe diaphragm in itself removes, in a great measure, all kinks orirregular portions.

With these and other objects and applications in view, my inventionfurther consists 1n the combination4 and 1n the details of constructionand arrangement hereinafter described and claimed and illustrated in theaccompanying drawing, wherein:

Figure 1 is an enlarged fragmentary top plan view of a diaphragmembodying my invention);

Fig. 2 is a sectional view taken on the line II-II of'Fig. l; A K

Figi 3 is a transverse sectional view of telephone apparatus embodyingmy. invention. i

In the drawing is shown a diaphragm 1 comprising a circular disk ofresilient ma'- terial provided withl corrugations 2 disposed inconcentric kcircles andhaving a central point 3 designed to serve as'thecenter of vibration of the disk by the connection ofV actuating meansthereto, as explained more fully hereinafter. The corrugations 2 may beso pressed into the disk 1. asl toform a substantially flat surface 4and raised surface 5. For reasons hereinbefore mentioned the relationbetween `the radii of the several concentric circles, as indicated by (1a2, etc., in Fig. 1, is the same as that between prime numbers expressedin the same units. lt has been found that improvedV results are obtainedby employing corrugations of relatively small dimensions, Lsayapproximately 0.012 inch radius.

While the diaphragm 1 is shown as prolill() vided with corrugations 2,it is apparent ,that a diaphragm having similar non-reso nantcharacteristics may be obtained by employing sti'ening or dampeningmeans arranged at distances from the center of vibration which are primeto each other.

lin a practical embodiment of my invention, the several radii al, a2,etc., are determined by the following series of prime num# bers, 19, 23,31,37, 43, 47, 53, 61, 67, etc., which may be expressed as distanceswith the inch as a unit by multiplying this series by the number .008.

lin order to better illustrate my invention, 1 have shown it embodied ina well known type of telephone receiver 6 but`, of course, it is not tobe limited to such structure or such specific application. As shown inFig. 3, the telephone receiver 6 comprises a casing 7 having acylindrical wall 8 and a base 9 therefor adapted to form a chamber 11open at its upper end. A circular cover plate member 12 having asubstantially.centrally disposed perforation 13 is provided to close theopen end of the chamber 11, the edges of said plate member 12 restingupon the upper end of the wall 8 of the casing 7. .A cap member 14 ofannular shape is provided with a threaded portion 15 for engaging asimilar threaded portion 16, which is disposed on the outer surface ofthe upper end of the wall 8, and with 'a shoulder portion 17 forengaging the edge of said plate member 12 which is resting upon saidwall 8, whereby the cover plate member 12 may be rigidly secured inposition.

A substantially circularly bent permanent I magnet 18 has it ends orpoles 19 arid 21 disposed in alinement parallel to the axis of thereceiver. The magnet 18 may be supported from the under surface of saidcover plate 12 in any approved manner (not shown). A pair of soft ironyoke members 22 and 23 are provided, having polar projections 24, 25 and26, 27, respectively.l rlhe yoke members .22 and 23 are rigidly securedto the ends 19 and 21, respectively, of the permanent magnet 18 in suchmanner that the polar projections of one magnet are in alinement withthe polar projections of the other magnet with an air gap 28.therebetween. l

A magnetizable armature member 29 is pivotally mounted in said air gaps28 at a point 29 midway between said polar projec- 'tions in anyapproved manner. @ne end of the armature member 29, adjacent to thepermanent magnet poles 19 and 21, may be connected to the polarprojections 27 by means-of a spring member 31 to admit of vibratoryaction'of the armature member 29. The other end of the armature member29 may be rigidly secured, by means of a con necting link 32 and aconnector 33, if@ lh@ Lasarte midpoint -3 of the diaphragm, which isdesigned to serve as the center'of vibration thereof. yllhe connectionlink 32 and connector 33 constitute portions of the subject matter of apending application of A. Nyman, Serial No. 556,856, iiled April 27,1922, and assigned to'the lVestinghouse .Electric t ManufacturingCompany. rlhe diaphragm 1 is disposed adjacent to the outer surface ofthe cover member 12 immediately over the perforation 13 with the flatsurface 4 preferably Vtoward the exterior. ln view of such construction,it can be seen that Jvibratory action of the armature member 29 isreadily transmitted to thefdiaphragm 1.

A magnetizing winding 34 is wound upon atubular core member 35 of aframe 36 which is so'mounted between the several polar projections as toproduce lines of induction which traverse paths indicated by the arrows6- upon the passage of currents through the winding 34 in one direction.When the direction of the currents reverses,

v the direction of the arrows is corresponding ly reversed. Theterminals of the winding 34 may be connected to external circuitterminals 37 and 38 which may be carried by the inner side of the coverplate member 12.

When modulating currents corresponding to a signal are caused totraverse the turns of the magnetizing winding 34, the armature member 29is vibrated in accordance with the varying intensity of such currents,as will be understoood by those versed in the art 'lhe vibration of thearmature member 29 is transmitted to the diaphragm 1 and hence causes,sound waves.

Among the several advantages of the diaphragm embodying my invention maybe mentioned the elimination -of so-called side tones, theu eliminationof distortion when the transmitter is worked hard, and other advantagesherein before set forth. 4

lWhile l: have shown but one embodiment of my invention, for the purposeof describing the same and illustrating its principles of operation, itis apparent that various changes and modiiications may be made in thenature and in the detailspf, construction without departing from thespirit of my invention. lf desire, therefore, that only such limitationsshall be-imposed thereon as are indicated in the appended claims ordemanded by the prior art.

1 claim as my invention:

1. A diaphragm comprising a plate provided with damping means spacedfrom a common point at distances having the same relation as primenumbers, said common point being the center of said plate.

2. A diaphragm comprising a plate provided with a plurality o fstiffening portions spaced from a central point at distances prime toeach other, said Point constituting the e'nter of sald plate,

3. A diaphragm comprisingL a plate provided with indentations disposedin spaced relation from a central point in said plate at distances primeto each other.

4. A diaphragm comprising a plate having a substantially. flat operativesurface provided with corrugations symmetrically disposed in spacedrelation from the center thereof at distances prime to each other.

5. A diaphragm comprising a substantially flat plate provided with aplurality of damping means concentrically disposed and in spacedrelation with respect to a common point on said plate at distances primeto each other.

6. A diaphragm comprising a plate provided with stiffening means,extending outwardly from the center of vibration of'said plate inconcentric circles, the radii of which are prime to each other.

7. A diaphragm comprising a plate provided with concentric rings ofcorrugations, the radii ofthe several rings with respect to the centerof said plate being prime to each other.

8. A diaphragm comprising a disk having a substantially flat operativesurface provided with a plurality of concentric rings o,f shallowindentations extending radially outwardly from'the center of vibrationof said disk, lthe radii of certain of said rings being in the samerelationas prime i numbers.

' radii of all of-said circles being prime to4 9. A diaphragm comprisinga disk having a low fundamental frequency and provided with a pluralityof indentations disposed in concentric circles extending outwardly fromthe center of said disk, the

each other.

l0. In a translating device, a casing adapted to form a chamber open atone end, a cover for said chamber having a perforation therein, meansfor clamping said cover rigidly in position and enclosing a spacetherebetween, and a mechanically vibratory diaphragm provided withconcentric rings of corrugations disposed therein and extendingoutwardly from the center thereof, the radii Iof said rings being primeto each other.

11. In a translating device, a casing adapted to form a chamber open atone end, a cover for said chamber having a perforation therein, meansfor clamping said cover rigidly in position, a diaphragm disposedadjacent the upper side of saidy cover immediately over saidperforation, said diaphragm comprising a disk provided with concentricrings of corrugations extending outwardly from the center thereof, theradii of which are prime to each other, and means for vibrating saiddiaphragm in accordance with a signal.

l12. In a translating device, a casing adapted to form a chamber open atone end, a cover for said chamber having a substantially centrallydisposed perforation, means for clamping said cover rigidly in positionenclosing a space therebetween, a diaphragm disposed in said space insuch manner that the center of vibration thereof is immediately abovesaid perforation, said diaphragm comprising a disk provided with dampingmeans vspaced from said center of vibration in the same relation asprime numbers, electrical signal current translating means disposed saidvcasing and a link adapted to be vibrated by said translating means inaccordance with signal currents extending through said perforation andrigidly secured to the center of vibration of said diaphragm.

13. In a translating device, a casing adapted to form a chamber vopen atone end, a cover for said chamber having a substantially centrallydisposed perforation, means for clamping said cover rigidly in positionenclosing a space, therebetween, a diaphragm comprising a disk providedwith corrugationsformed 'therein in such manner as to provide asubstantially flat surface on one side and a raised surface on theopposite side, said diaphragm being so disposed .in said space' that theflat surface faces the clamping means and the center of vibration isimmediately above said perforation, said corrugationsbeing spaced fromthe center of vibration of said diaphragm in the same relation as primenumbers, electrical signalcurrent translating means disposed in saidcasing and a link adapted/to be vibrated by said translating means inaccordance with signal currents extending through said perforation andrigidly secured to the center of vibration ofsaid diaphragm.

In testimony `whereof, I have hereunto subscribed my name this 17 th dayof April, 1922.

PHILLIPS THOMAS.

